High frequency circuits



Dec. 2, 1941. a E E I 2,264,879

HIGH FREQUENCY CIRCUITS Filed Aug. 26, 1939 I Maw ATTOEAE'Y Patented Dec. 2, 1941 HIGH FREQUENCY CIRCUITS Erich Heinecke, Berlin, Germany, assignor to O. Lorenz Aktiengesellschaft, Bcrlin-Tempelhof,

Germany Application August 26, 1939, Serial No. 292,059

In Germany June 30, 1938 3 Claims.

This invention relates to circuit arrangements in electron tube devices, and more particularly to new and useful means for coupling two tubes in ultra-high frequency operation.

My invention consists in certain features of novelty which will be fully understood from the following description and be pointed out in the appended claims, reference being made to the accompanying drawing, in which Fig. 1 is a diagram theoretically explanatory of the art, Fig. 2 shows a circuit arrangement explanatory of my invention, while Fig. 3 is a circuit diagram according to this invention.

It is frequently desirable in high and ultrahigh frequency multi-stage amplifiers to interconnect two electron discharge tubes of the individual stages through means, such as a voltage divider, which as indicated in the theoretical circuit of Fig. 1, involves a constant voltage ratio of UI U2 at all frequencies to which L, C, and C2 are tuned. The voltages across the condensers Cl and C2 in this figure are proportional to the respective impedances. This ratio is given by the following expression:

which shows that the frequency w exerts no influence since in the numerator cancels w in the denominator. A variometer L is inserted which in conjunction with condenser C1, C2 tunes the circuit to the operating frequency. As a matter of fact, the plate of the first tube requires a plate potential and the grid of the second tube requires a negative biasing potential in order to provide an operative circuit, which potentials are applied to the respective electrodes through choking coils DI and D2, respectively, as shown in the Fig. 2. The presence of these coils unbalances the previously mentioned condition, so that by omitting factors which are irrelevant from the present discussion, the voltage ratio may be expressed as follows:

Ul 1 U2 (00] 2 in which where we is 2 1r times a frequency different from the operating frequency and z defines the impedance. It is thus obvious that the voltage ratio strongly depends upon frequency.

This disadvantage is eliminated according to my invention by the provision of a voltage divider which is independent of frequency and which is so designed that the plate potential choke coil DI together with the condenser Cl forms one oscillatory circuit across the tube I, and the grid potential choke coil D2 together with the condenser C2 likewise constitutes an oscillatory circuit across the grid circuit of the second tube 2 as shown in Fig. 3. These two oscillatory circuits by suitable choice of the respective choke coils are tuned to the same frequency me, which, however, differs from the operating frequency. If the factor zl defines the impedance of Cl, DI, and. 22 designates the impedance C2, D2 the voltage formula will be:

U2 2/22 and since is in the numerator cancels 7'22 in the denominator, the frequency independency is restored in the voltage divider.

What is claimed is:

1. In a circuit arrangement comprising a first and a second electron discharge device, each having an input and an output and adapted to operate at given high and ultra-high frequencies, a voltage divider for coupling the output circuit of the said first discharge device with the input circuit of the said second discharge device and comprising, an oscillatory circuit across the output circuit of the said first tube, a further oscillatory circuit across the input circuit of the said second tube, the said oscillatory circuits being tuned to the same frequency and said frequency being different from the operating frequency, and a series branch interposed between the said oscillatory circuits for tuning the circuit arrangement to the operating frequency.

2. A circuit arrangement as defined in claim 1, in which the impedance of one of said oscillatory circuits differs from the impedance of the other of said oscillatory circuits.

3. A circuit arrangement according to claim 1, in which a. choke coil is provided in each oscillatory circuit for tuning the said circuits to the same desired frequency.

ERICH HEINECKE. 

